1. Field of the Invention
The present invention relates to a crankshaft for an in-line four cylinder engine.
2. Description of Related Art
A crankshaft for an in-line four cylinder engine includes: crank journals serving as a rotational center of the crankshaft; crank pins disposed at positions eccentric to the corresponding crank journals, and to which connecting rods are coupled; and crank arms that couple the respective crank journals to the corresponding crank pins.
Insufficient rigidity of crankshafts causes vibrations or the like during rotation thereof; therefore, partial reinforcement is often provided to the crankshafts so as to secure sufficient rigidity. An example of such partial reinforcement for securing the rigidity may include a crankshaft described in Japanese Patent Application Publication No. 2012-172797. In the crankshaft described in JP 2012-172797 A, in order to suppress generation of torsional vibrations at the crank arms near a flywheel because of vibrations of the flywheel disposed at a shaft end of the crankshaft, the crank arms near the flywheel are provided with partial reinforced portions so as to enhance rigidity of the crank arms.